The present invention relates to imaging systems and in particular to imaging systems capable of acquiring image data over a wide-angle field.
For security and other purposes there is often a requirement for a surveillance system which can be used to examine a wide-angle field of view, often up to a full 360xc2x0 panorama. GB2157526 describes an imaging system having a platform which is rotatable about an azimuthal axis and which carries an image data collection sensor having a fixed field of view. The platform is continuously rotated about the axis to scan the sensor field of view around a 360xc2x0 panorama at a fixed elevational angle. Normally, data is acquired between two angular positions for display at a display station. There exists a trade-off between the spacing of these two angular positions and the resolution of the data acquired and displayed.
A problem with the system of GB2157526 is the lack of flexibility and the lack of redundancy provided.
It is an object of the present invention to provide an imaging system which overcomes or at least mitigates disadvantages of the above system.
According to a first aspect of the present invention there is provided an imaging system comprising an image-data collection station which is rotatable about an azimuthal axis, the image data collection station comprising at least two circumferentially spaced apart image sensors arranged for rotation with the station and sensor control means for selectably and independently turning the sensors on and off during a rotation of the data collection station.
It will be appreciated that, as the first aspect of the present invention provides a plurality of image sensors, embodiments of the present invention have a degree of built-in redundancy, e.g. if one sensor fails another sensor can still be used to collect image data from an area of interest. In the event that one or a proportion of the image sensors fail, the result will not be a complete loss of image data. Embodiments also provide for increased flexibility. For example, where the bandwith (or capacity) of one sensor is fully used to look at a first selected area, a second sensor can be used to look at a second area or to provide a higher update rate in part or all of the first selected area.
According to a second aspect of the present invention there is provided an imaging system comprising an image-data collection station which is rotatable about an azimuthal axis, the image data collection station comprising at least two circumferentially spaced image sensors arranged for rotation with the station, wherein at least one of the image sensors has a variable field of view and/or comprises means for varying the angle of elevation of the sensor.
Embodiments of the second aspect of the present invention enable the sensors to follow the same or different elevational paths around the azimuthal axis. This may be achieved by providing means for varying the elevation angle of a sensor. Where the paths followed by two image sensors are the same and the sensors have the same field of view, the data from the two sensors can be combined to provide enhanced image resolution over an entire captured image. Where the elevational paths followed by the two sensors differ, the image data provided by the sensors may be displayed on separate displays or may be combined to provide a wider overall field of view on a single display.
In one embodiment, at least one of the sensors comprises a zoom lens which can be zoomed-in on an area of particular interest. The resulting image data can either be displayed independently of image data captured by other sensors or can be used to selectively enhance the resolution of a region of an image captured by another image sensor having a wider field of view.
Preferably, the imaging system comprises an image monitoring station having control means for independently controlling the magnification of image sensor zoom lenses and/or the elevational angle of the image sensors. The control means comprises a tracking computer for identifying a target within an image and for direction one or more of the image sensors to track the identified target by dynamically controlling the elevation angle and/or zoom of the sensors. The control means is arranged to combine image data received from the or each tracking image sensor and from a further image sensor having a wider field of view which contains the target, whereby an image can be obtained in which the target is shown with an increased resolution relative to the remainder of a larger field of view image.
Preferably, the image sensors are spaced at regular angular intervals around the image data collection station.
Preferably, the image data collection station comprises at least four image sensors.
it will be appreciated that a particularly advantageous imaging system is achieved by combining both the first and second aspects of the present invention.